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Activated Clotting Time Monitoring during Osteocutaneous Free Fibula Flap Surgery

2015; Lippincott Williams & Wilkins; Volume: 135; Issue: 2 Linguagem: Inglês

10.1097/prs.0000000000000906

1529-4242

Nirav Patel, Dhruv Singhal,

Antiplatelet Therapy and Cardiovascular Diseases

Sir: Routine use of intraoperative systemic heparin during microsurgical reconstruction is not indicated. However, systemic heparinization is used by the microsurgeon in specific cases such as an intraoperative vessel thrombosis or a documented hypercoagulable state.1 Intraoperative monitoring of heparinization with activated clotting time is the criterion standard in vascular and cardiac surgery. Since the 1970s, activated clotting time monitoring has become routine in peripheral vascular surgery, with target levels of 180 to 200 seconds.2 Moreover, in cardiac surgery, routine activated clotting time monitoring during cardiopulmonary bypass is associated with decreased postoperative blood loss.3 Activated clotting time monitoring during microsurgical reconstruction has not been previously reported. In this report, activated clotting time monitoring was used intraoperatively to monitor the effectiveness of systemic heparin in a known hypercoagulable patient undergoing mandibular reconstruction with a free fibula osteocutaneous flap. Activated clotting time monitoring resulted in higher than normal administration of systemic heparin and assisted the hematology service in diagnosing an additional hematologic abnormality. The patient was a 72-year-old woman (61 kg) with a recently diagnosed T4N0Mx squamous cell carcinoma of the left retromolar trigone region with anterior extension along the buccal mucosa and radiographic evidence of bone invasion (Fig. 1). Of note, the patient’s medical history was significant for myelofibrosis treated with Jakafi chemotherapy. The patient was diagnosed with essential thrombocythemia and had suffered a previous deep venous thrombosis and pulmonary embolism. The patient was followed closely by the hematology service, and a Lovenox (Sanofi-Aventis, Paris, France) bridge was recommended. Preoperatively, a surgical decision was made to systemically heparinize the patient before clamping of the donor peroneal vessels. The activated clotting time machine (Fig. 2) was brought into the operating room at the start of the case with the plan to keep the activated clotting time levels at 200 seconds. After the initial administration of 6000 units of systemic heparin, the patient’s activated clotting time levels remained unchanged. Ultimately, the patient would require 21,000 units of heparin to achieve the desired activated clotting time levels. A postoperative heparin drip was maintained and managed by the hematology service. The high levels of intraoperative heparinization required to achieve acceptable activated clotting time levels led to a further workup for antithrombin III deficiency, which was positive. Of note, the patient did develop a postoperative common femoral vein clot of the ipsilateral lower extremity requiring the placement of an inferior vena cava filter. The patient’s other postoperative issues have included the need for a cholecystostomy tube and partial-thickness native neck flap necrosis treated with débridement and a pedicled myocutaneous flap. The free fibula flap healed entirely without any issues.Fig. 1: Intraoperative photograph demonstrating a 7-cm defect of the left mandibular body and ramus. The soft-tissue defect included the soft palate, retromolar trigone, and floor of mouth.Fig. 2: Lightweight and easily portable equipment for monitoring activated clotting time intraoperatively. The compact device measures 19 × 5 × 10 cm. Device setup and measurement require 5 minutes, thereby providing almost immediate feedback to the microsurgeon regarding the effectiveness of heparinization.The use of systemic heparin in free flap reconstruction is effective in specific cases.1 Currently, there is no standard heparin dose recommended for these cases. The routine use of activated clotting time monitoring when systemic heparin is administered would offer the microsurgeon immediate feedback regarding the level of therapeutic anticoagulation and potentially alert the surgeon to an underlying hypercoagulable state. Although a target activated clotting time level of 200 seconds was chosen in this case, the optimal activated clotting time levels for free flap procedures remain to be seen. DISCLOSURE The authors have no financial interest to declare in relation to the content of this article. Nirav Patel, B.S. Dhruv Singhal, M.D. Department of Surgery Division of Plastic and Reconstructive Surgery University of Florida Health System University of Florida Medical School Gainesville, Fla.